This invention relates to an iron base alloy having a high lubricating characteristic and excellent wear resistance.
In general, compounds of sulphur or selenium with a metal selected from Group IVb, Vb and VIb of the periodic table are known to be excellent lubricants. Examples are compounds with titanium (TiS.sub.2, TiSe.sub.2), compounds with zirconium (ZrS.sub.2, ZrSe.sub.2), compounds with vanadium (VS.sub.2, VSe.sub.2), compounds with tantalum (TaS.sub.2, TaSe.sub.2), compounds with molybdenum (MoS.sub.2, MoSe.sub.2) and compounds with tungsten (WS.sub.2 WSe.sub.2). These compounds have a low friction characteristic and are used in practice as lubricants in the following forms:
1. A SOLID COATING APPLIED ON THE SURFACE OF A MATERIAL TO BE SUBJECTED TO FRICTION;
2. A SOLID COMPOSITE MATERIAL IN WHICH THE SULPHIDE OR SELENIDE IS BONDED IN THE FORM OF A LAYER ON A BASE METAL USING AN ADHESIVE SUCH AS AN ORGANIC RESIN; AND
3. A SOLUTION IN A LIQUID LUBRICANT.
However, the compounds listed when used as described above have the following serious drawbacks, the drawbacks being listed in the same order as above:
(1) A coating tends to flake or peel from a base metal so that the lubrication characteristic decreases with wear.
(2) When incorporated in a resin, the compounds have a low heat resistance, so that friction which raises the temperature of the composition results in thermal decomposition.
(3) Segregation of the selenide or sulphide in the liquid is likely to occur, as a result of which the lubricating at the frictional interface, so that severe wear of the metal which it is desired to protect may occur.
As is disclosed in the aforenoted application the present inventors overcame the listed drawbacks by providing a base metal alloy having a low coefficient of friction. In pursuit of this objective it was established that an iron base alloy containing from 5% to 30% (by weight, and the same hereinafter) of one or more metals of titanium, zirconium, vanadium, niobium, tantalum, molybdenum and tungsten, and from 0.5% to 5% of either sulphur or selenium could provide the excellent lubricating characteristic. In the above iron base alloy, the base metal itself has a lubricating characteristic thereby eliminating the danger of flaking or peeling which arises when a coating of a lubricant is used. However, such alloys could benefit from increased wear resistance.